(a) Field of the Invention
The present invention relates to an RFID reader antenna to which a diversity technology is applied.
(b) Description of the Related Art
An ultra high frequency (UHF) band radio frequency identification (RFID) system may be configured of a tag (or transponder) and a reader (or interrogator). A fading phenomenon generally occurs due to many scattered waves under the environment that an RFID system is operated. In particular, when an RFID system is constructed in workshops of metal environment such as vehicle, ship, aviation fields, fading occurring due to scattering of many electromagnetic waves may suddenly reduce system recognition. As such, a method for improving RFID recognition in the environment that electromagnetic waves are poor requires an RFID reader technology having a transmitting or receiving diversity function
A transmitting or receiving diversity method may be largely classified into a spatial diversity method for overcoming fading by maintaining a distance between a plurality of antennas at a specific distance, a polarization diversity method for overcoming fading by making polarizations of a plurality of antennas different, and a radiation pattern diversity method for overcoming fading by making radiation patterns of antennas different.
As the existing RFID reader antenna, a transmitting/receiving separable antenna in which a transmitting port and a receiving port are separated or a transmitting/receiving antenna in which a transmitting port and a receiving port are implemented in one antenna has been used. However, to implement the RFID reader having a diversity function, a plurality of element antennas are required at a transmitting or receiving terminal. Further, when the plurality of element antennas are used for transmission or reception, if an isolation between the element antennas is not secured, a correlation between signals transmitted to or received from each element antenna is increased and thus a diversity effect may not be obtained.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.